Data storage system with light beam write/readout



J. T. MCNANEY May 4, 1965 DATA STOAGE SYSTEM LIGHT BEAM WRITE/READOUT 2 Sheets-Sheet 1 Filed July 5, 1960 I6 INVENTOR.

JOSEPH T. McNANEv.

May 4 1965 J. T. MGNANEY 3,182,223

DATA STORAGE SYSTEM WITH LIGHT BEAM WRITE/READOUT Filed July 5, 1960 2 Sheets-Sheet 2 *f [Il I: Q -Ll 5 INVENTORm JOSEPH T. McNANEv.

United States Patent O 3,182,223 DATA STRAGE SYSTEM WITH LEGHT BEAM WRITE/READOUT Joseph T. MeNaney, La Mesa, Calif., assigner to General Dynamics Corporation, Rochester, NX., a corporation of Delaware Filed July 5, 196i), Ser. No. 40,794 2 Claims. (Cl. S15-lil) This invention relates to a data storage system, and more particularly to one that stores data in the form of an electrical charge pattern on the surface of a photoconductor.

It is freqeuntly desired to store data, and to later read it out in the same or other forms. lFor exam-ple, the incoming data may be in the form of light pulses or a picture and the output may be preferred in the form of electrical impulses. At o-ther times the input may be in the iorrn ot a P.iP.I. radar display, and it may be desired that the output be a raster-type display-for producing a brighter display or multiple displays on a plurality of monitors.

It is therefore the principal object of my invention to provide an improved storage display and readout system.

The attainment of this object and others will be realized from the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 illustrates the basic concept of my invention; and

FIGURES 2 through 8 show various embodiments thereof. 'i

In FIGURE 1, which shows the basic concept of my invention, data is written in in the `forming of an electrical charge pattern, and read out .by a scanning light beam. To accomplish this result, I use a structure that comprises a sheet 1'2 of photoconductive material that is in contiguous relation with a layer 14 of transparent electrically-conductive material. The dat-a to be stored is rst written onto photoconductor 12 in the form of a charge pattern, which is produced by means to be discussed later. As is Well known, photoconductive material becomes conductive where illuminated, and I use this characteristic to read out the stored information by causing a light beam to impinge upon sheet 12 from either direction. The conductive illuminated area of photoconductor I12 permits the charges that form the charge pattern to leak. olf through the conductive areas to conductor 14. The leakage produces, at output terminal 16, an output signal that may be used in any desired manner.

FIGURE 2 shows an embodiment that uses a doubleended cathode ray tube having a common faceplate. In this embodiment the electron .beam from the right hand cathode ray tube produces a charge pattern on photoconductive material 12 by either depositing electrons thereon, or by causing electrons to be emitted by secondary emission.

Readout is achieved by causing the electron beam in the left hand cathode ray tube to impinge on a phosphor screen 18, the light from which permits the charge pattern to be dissipated as previously described. The light spot produced on phosphor screen 18 of the left hand tube traces out a raster comprising a series `of parallel lines; and the instantaneous output signal corresponds with the position of .the readout spot of light. It will be noted that in this embodiment the information is written in electrically, and read out electrically.

FIGURE 3 shows an embodiment wherein the writing and the reading are done by the same cathode ray tube. In this embodiment photo-conductive material 12 is rst given a uniform charge in any convenient manner. The

3,182,223 Patented May 4, 1965 ICC cathode ray tube is then energized to produce a display on phosphor screen l18, and the light traversing optical liber faceplate S--which is used for improved resolutiondischarges selected areas of the photocond-uctor to produce a `charge pattern. This pattern may be stored tor as long as desired, land when it is desired to read it out, the cathode ray tube is again energized. The moving spot of light permits the charge pattern to leak oli, in this way producing output signals.

The embodiment of lFIGURE 4 uses two separate tubes and a structure 1l) comprising a photoconductive sheet 12 and an electrically conductive layer 14. Adjacently positioned is another transparent structure 2t) for producing a uniform charge on the photoco-nductive material. Charging structure 20 may use corona discharge, electrostatic induction or any other suitable method. lFor example, to produce a corona discharge, .charging switch 15 is closed. lA discharge takes place between elements 20 and 12, resistance 17 completing the circuit. During tls charging interval, output switch 19 is open, so no output signal appears at output terminal 16.

To write in the message, switches 15 and 19 are opened, and t-he right hand tube writes as previously explained. During this writing interval, part of the uniform charge on photoconductor 12 leaks off to produce a charge pattern; the leakage current passing ot through resistance 17.

lIn order to readout, switch 15 is opened and switch 19 is closed. Readout is produced by the left hand cathode ray tube, whose beam ot light scans the pho-tocchductive material and permits the charge pattern to leal: olf; the leakage through resistance 17 producing an output signal at output terminal 16. The operation of FIG- URE 4 is thus a sequential one wherein a uni-form charge is first produced on photoconductor 12, parts of the unifor-rn charge are permitted to leak off to produce a charge pattern, and the charge pattern is then read out by another cathode ray tube.

One use lfor the embodiment of FIGURE 4 is to convert a PPJI. display on one tube to signals that provide a raster-type display.

The embodiment of FlGURE 5 shows another method of producing a charge pattern. This embodiment uses optical fibers 22 that are coated with sleeves 24 of photoconductive material. When light enters. selected fibers, their circumjacent photoconductive sleeves are illuminated, and the resultant low electrical resistance permits a potential applied to transparent electrical coating 26 to appear at the other end of the photoconductive sleeve. There a corona discharge is produced, and this results in a charge pattern being produced on photoconductive material 12. Alternatively, `a uniform charge may be produced, and the corona discharge from the optical bers used to produce the charge pattern by selective neutralization. The charge pattern may be read out by a cathode ray tube or a scanning beam of light, and an output signal is obtained as previously described. In this embodiment Writing and readout are performed by light.

Referring now to FIG. 6, there is shown an embodiment of my invention wherein a moving strip 28 of material has the characteristic that a charge pattern produced on its surface will remain there for a desired period of time. To produce this charge pattern, I use a series of aligned charging elements 3i), such as Wires or pins. Potentials applied to selected elements will produce a discharge between the selected pin and the grounded electrode; the discharge resulting in a charge pattern on the surface of material 28. As material 2:8 moves downward as indicated by the arrow, the charge pattern passes in front of structure 10 that comprises a sheet of photoconductive material and a layer of transparent conductive material, as previously described. In the embodiment of FIGURE 6, the readout spot of light originates at the faceplate of a cathode ray tube, and produces output signals that correspond with the position of the light.

In the embodiment of FIGURE 7, the storage strip 32 comprises a sheet 12 of photoconductive material and a layer 14 of transparent electrically conductive material in a contiguous relationship. A transversely positioned corona producing element or Wire 34 provides the photoconductive surface with a uniform electrical charge. As the uniformly charged strip passes in front of the first cathode ray tube, light therefrom causes selective areas of the photoconductive material to become conductive, and selected charges leak off through the transparent electrically conductive material 14. As the storagestrip moves beyond the first cathode ray. tube,

its surface therefore contains a charge pattern which may be picture, characters, codes or any other desired pattern. -As this charge pattern passes in frontV of the second cathode ray tube, the light beam thereof reads out the information by illuminating the photoconductive material; and the charge pattern therefore leaks off, vthus producing an output signal.

The embodiment of FIGURE 8 comprises a structure electricalconductor 14. A charge producing element 20 Yoperates as previously described to produce a uniform charge on thepsurface of photoconductor 12. Light impinges on photoconductor 12, to permit leakage of charges from selective areas, thus producing a charge pattern as previously described.

In order to read out the stored data, I use a sheet 36 of electroluminescent material, which has sets 38 and 40 of crossed grids sandwiched to the sides thereof. By suitably energizing selected crossed grids, a potential is applied across a small area of the electroluminescent material, in this way producing movable spots of light that permit the charge pattern to produce output signals as previously described. In this Way, an electroluminescent structure is used for the readout.

The particular embodiment of the invention illustrated and described hereinpis illustrative only and the invention includes such other modifications and equivalents as may readily appear to those skilled in the art, within the scope of the appended claims.

1 claim:

1. In combination, a single sheet of electrically insulating photoconductive material capable of maintaining a charge pattern on a surface thereof, means including a charging structure for producing a uniform distribution of electrons on said surface of said sheet, an electrically conductive layer positioned contiguously with said sheet,

and said output impedance means for establishing an i electrical charge image on said sheet, means for scanning said surface of said sheet with light information to remove said electrical charge image from said sheet, said output impedance means accommodating an electron How accompanying the removal of said charge image for providing an output signal voltage at said output terminal means, said charge pattern producing means, and said means for scanning being embodied Within a singl cathode ray tube. Y

2. An information handling system comprising, a composite two-sheet information storage plate consisting essentially of a transparent electrically conductive sheet and a sheet of photoconductive material having an ex.- posed side anda side in contact with said transparent electrically conductive sheet, means for producing an electrostatic image on the exposed side of said sheet of photoconductive material which electrostatic image is stored thereon, a load circuit for manifesting current changes therethrough, means for coupling said load circuit to said transparent electrically conductive sheet, and means for sweeping said sheet of photoconductive material with a beam of light to cause current to ow through said load circuit representative of said electrostatic image. Y

References Cited by the Examiner UNITED STATES PATENTSr 2,465,093 6/ 46 Hansen et al. Z50-49.5 2,674,704 4/ 54 Weimer 3 15-12 2,698,915 1/55 Piper 178,-.6 2,787,724 4/57 Webley 315-12 2,790,929 4/57 Herman et al. 315-12 2,856,533 10/58 Rosenthal 346-74 X 2,864,031 12/58 Smith 315-12` 2,899,448 8/59 Kalfaian 315-10 2,916,661 12/59 Davis 315-12 2,918,600 12/59 Pensak 315-12 X 2,928,973 3/60 Crews 315-12 X 2,965,783 12/60 Jaffe 178-6 3,011,019 11/61 Rado 178-7.1 3,029,717 4/ 62 Hildebrandt 178-6 3,043,910 7/ 62 Hicks 178-7.85 3,069,551 12/62 Haine 315-10 XV DAVID G. REDINBAUGH, Primary Examiner.

RALPH G. NILSON, ROY LAKE, Examiners. 

2. AN INFORMATION HANDLING SYSTEM COMPRISING, A COMPOSITE TWO-SHEET INFORMATION STORAGE PLATE CONSISTING ESSENTIALLY OF A TRANSPARENT ELECTRICALLY CONDUCTIVE SHEET AND A SHEET OF PHOTOCONDUCTIVE MATERIAL HAVING AN EXPOSED SIDE AND A SIDE IN CONTACT WITH SAID TRANSPARENT ELECTRICALLY CONDUCTIVE SHEET, MEANS FOR PRODUCING AN ELECTROSTATIC IMAGE ON THE EXPOSED SIDE OF SAID SHEET OF PHOTOCONDUCTIVE MATERIAL WHICH ELECTROSTATIC IMAGES IS STORED THEREON, A LOAD CIRCUIT FOR MANIFESTING CURRENT CHANGES THERETHROUGH, MEANS FOR COUPLING SAID LOAD CIRCUIT TO SAID TRANSPARENT ELECTRICALLY CONDUCTIVE SHEET, AND MEANS FOR SWEEPING SAID SHEET OF PHOTOCONDUCTIVE MATERIAL WITH A BEAM OF LIGHT TO CAUSE CURRENT TO FLOW THROUGH SAID LOAD CIRCUIT REPRESENTATIVE OF SAID ELECTROSTATIC IMAGE. 